projects/linux·blob v3.5-rc1 · refs

455 lines · 9.2 KiB

1/*
2 * devtmpfs - kernel-maintained tmpfs-based /dev
3 *
4 * Copyright (C) 2009, Kay Sievers <[email protected]>
5 *
6 * During bootup, before any driver core device is registered,
7 * devtmpfs, a tmpfs-based filesystem is created. Every driver-core
8 * device which requests a device node, will add a node in this
9 * filesystem.
10 * By default, all devices are named after the name of the device,
11 * owned by root and have a default mode of 0600. Subsystems can
12 * overwrite the default setting if needed.
13 */
14
15#include <linux/kernel.h>
16#include <linux/syscalls.h>
17#include <linux/mount.h>
18#include <linux/device.h>
19#include <linux/genhd.h>
20#include <linux/namei.h>
21#include <linux/fs.h>
22#include <linux/shmem_fs.h>
23#include <linux/ramfs.h>
24#include <linux/sched.h>
25#include <linux/slab.h>
26#include <linux/kthread.h>
27
28static struct task_struct *thread;
29
30#if defined CONFIG_DEVTMPFS_MOUNT
31static int mount_dev = 1;
32#else
33static int mount_dev;
34#endif
35
36static DEFINE_SPINLOCK(req_lock);
37
38static struct req {
39 struct req *next;
40 struct completion done;
41 int err;
42 const char *name;
43 umode_t mode; /* 0 => delete */
44 struct device *dev;
45} *requests;
46
47static int __init mount_param(char *str)
48{
49 mount_dev = simple_strtoul(str, NULL, 0);
50 return 1;
51}
52__setup("devtmpfs.mount=", mount_param);
53
54static struct dentry *dev_mount(struct file_system_type *fs_type, int flags,
55 const char *dev_name, void *data)
56{
57#ifdef CONFIG_TMPFS
58 return mount_single(fs_type, flags, data, shmem_fill_super);
59#else
60 return mount_single(fs_type, flags, data, ramfs_fill_super);
61#endif
62}
63
64static struct file_system_type dev_fs_type = {
65 .name = "devtmpfs",
66 .mount = dev_mount,
67 .kill_sb = kill_litter_super,
68};
69
70#ifdef CONFIG_BLOCK
71static inline int is_blockdev(struct device *dev)
72{
73 return dev->class == &block_class;
74}
75#else
76static inline int is_blockdev(struct device *dev) { return 0; }
77#endif
78
79int devtmpfs_create_node(struct device *dev)
80{
81 const char *tmp = NULL;
82 struct req req;
83
84 if (!thread)
85 return 0;
86
87 req.mode = 0;
88 req.name = device_get_devnode(dev, &req.mode, &tmp);
89 if (!req.name)
90 return -ENOMEM;
91
92 if (req.mode == 0)
93 req.mode = 0600;
94 if (is_blockdev(dev))
95 req.mode |= S_IFBLK;
96 else
97 req.mode |= S_IFCHR;
98
99 req.dev = dev;
100
101 init_completion(&req.done);
102
103 spin_lock(&req_lock);
104 req.next = requests;
105 requests = &req;
106 spin_unlock(&req_lock);
107
108 wake_up_process(thread);
109 wait_for_completion(&req.done);
110
111 kfree(tmp);
112
113 return req.err;
114}
115
116int devtmpfs_delete_node(struct device *dev)
117{
118 const char *tmp = NULL;
119 struct req req;
120
121 if (!thread)
122 return 0;
123
124 req.name = device_get_devnode(dev, NULL, &tmp);
125 if (!req.name)
126 return -ENOMEM;
127
128 req.mode = 0;
129 req.dev = dev;
130
131 init_completion(&req.done);
132
133 spin_lock(&req_lock);
134 req.next = requests;
135 requests = &req;
136 spin_unlock(&req_lock);
137
138 wake_up_process(thread);
139 wait_for_completion(&req.done);
140
141 kfree(tmp);
142 return req.err;
143}
144
145static int dev_mkdir(const char *name, umode_t mode)
146{
147 struct dentry *dentry;
148 struct path path;
149 int err;
150
151 dentry = kern_path_create(AT_FDCWD, name, &path, 1);
152 if (IS_ERR(dentry))
153 return PTR_ERR(dentry);
154
155 err = vfs_mkdir(path.dentry->d_inode, dentry, mode);
156 if (!err)
157 /* mark as kernel-created inode */
158 dentry->d_inode->i_private = &thread;
159 dput(dentry);
160 mutex_unlock(&path.dentry->d_inode->i_mutex);
161 path_put(&path);
162 return err;
163}
164
165static int create_path(const char *nodepath)
166{
167 char *path;
168 char *s;
169 int err = 0;
170
171 /* parent directories do not exist, create them */
172 path = kstrdup(nodepath, GFP_KERNEL);
173 if (!path)
174 return -ENOMEM;
175
176 s = path;
177 for (;;) {
178 s = strchr(s, '/');
179 if (!s)
180 break;
181 s[0] = '\0';
182 err = dev_mkdir(path, 0755);
183 if (err && err != -EEXIST)
184 break;
185 s[0] = '/';
186 s++;
187 }
188 kfree(path);
189 return err;
190}
191
192static int handle_create(const char *nodename, umode_t mode, struct device *dev)
193{
194 struct dentry *dentry;
195 struct path path;
196 int err;
197
198 dentry = kern_path_create(AT_FDCWD, nodename, &path, 0);
199 if (dentry == ERR_PTR(-ENOENT)) {
200 create_path(nodename);
201 dentry = kern_path_create(AT_FDCWD, nodename, &path, 0);
202 }
203 if (IS_ERR(dentry))
204 return PTR_ERR(dentry);
205
206 err = vfs_mknod(path.dentry->d_inode,
207 dentry, mode, dev->devt);
208 if (!err) {
209 struct iattr newattrs;
210
211 /* fixup possibly umasked mode */
212 newattrs.ia_mode = mode;
213 newattrs.ia_valid = ATTR_MODE;
214 mutex_lock(&dentry->d_inode->i_mutex);
215 notify_change(dentry, &newattrs);
216 mutex_unlock(&dentry->d_inode->i_mutex);
217
218 /* mark as kernel-created inode */
219 dentry->d_inode->i_private = &thread;
220 }
221 dput(dentry);
222
223 mutex_unlock(&path.dentry->d_inode->i_mutex);
224 path_put(&path);
225 return err;
226}
227
228static int dev_rmdir(const char *name)
229{
230 struct nameidata nd;
231 struct dentry *dentry;
232 int err;
233
234 err = kern_path_parent(name, &nd);
235 if (err)
236 return err;
237
238 mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
239 dentry = lookup_one_len(nd.last.name, nd.path.dentry, nd.last.len);
240 if (!IS_ERR(dentry)) {
241 if (dentry->d_inode) {
242 if (dentry->d_inode->i_private == &thread)
243 err = vfs_rmdir(nd.path.dentry->d_inode,
244 dentry);
245 else
246 err = -EPERM;
247 } else {
248 err = -ENOENT;
249 }
250 dput(dentry);
251 } else {
252 err = PTR_ERR(dentry);
253 }
254
255 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
256 path_put(&nd.path);
257 return err;
258}
259
260static int delete_path(const char *nodepath)
261{
262 const char *path;
263 int err = 0;
264
265 path = kstrdup(nodepath, GFP_KERNEL);
266 if (!path)
267 return -ENOMEM;
268
269 for (;;) {
270 char *base;
271
272 base = strrchr(path, '/');
273 if (!base)
274 break;
275 base[0] = '\0';
276 err = dev_rmdir(path);
277 if (err)
278 break;
279 }
280
281 kfree(path);
282 return err;
283}
284
285static int dev_mynode(struct device *dev, struct inode *inode, struct kstat *stat)
286{
287 /* did we create it */
288 if (inode->i_private != &thread)
289 return 0;
290
291 /* does the dev_t match */
292 if (is_blockdev(dev)) {
293 if (!S_ISBLK(stat->mode))
294 return 0;
295 } else {
296 if (!S_ISCHR(stat->mode))
297 return 0;
298 }
299 if (stat->rdev != dev->devt)
300 return 0;
301
302 /* ours */
303 return 1;
304}
305
306static int handle_remove(const char *nodename, struct device *dev)
307{
308 struct nameidata nd;
309 struct dentry *dentry;
310 struct kstat stat;
311 int deleted = 1;
312 int err;
313
314 err = kern_path_parent(nodename, &nd);
315 if (err)
316 return err;
317
318 mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
319 dentry = lookup_one_len(nd.last.name, nd.path.dentry, nd.last.len);
320 if (!IS_ERR(dentry)) {
321 if (dentry->d_inode) {
322 err = vfs_getattr(nd.path.mnt, dentry, &stat);
323 if (!err && dev_mynode(dev, dentry->d_inode, &stat)) {
324 struct iattr newattrs;
325 /*
326 * before unlinking this node, reset permissions
327 * of possible references like hardlinks
328 */
329 newattrs.ia_uid = 0;
330 newattrs.ia_gid = 0;
331 newattrs.ia_mode = stat.mode & ~0777;
332 newattrs.ia_valid =
333 ATTR_UID|ATTR_GID|ATTR_MODE;
334 mutex_lock(&dentry->d_inode->i_mutex);
335 notify_change(dentry, &newattrs);
336 mutex_unlock(&dentry->d_inode->i_mutex);
337 err = vfs_unlink(nd.path.dentry->d_inode,
338 dentry);
339 if (!err || err == -ENOENT)
340 deleted = 1;
341 }
342 } else {
343 err = -ENOENT;
344 }
345 dput(dentry);
346 } else {
347 err = PTR_ERR(dentry);
348 }
349 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
350
351 path_put(&nd.path);
352 if (deleted && strchr(nodename, '/'))
353 delete_path(nodename);
354 return err;
355}
356
357/*
358 * If configured, or requested by the commandline, devtmpfs will be
359 * auto-mounted after the kernel mounted the root filesystem.
360 */
361int devtmpfs_mount(const char *mntdir)
362{
363 int err;
364
365 if (!mount_dev)
366 return 0;
367
368 if (!thread)
369 return 0;
370
371 err = sys_mount("devtmpfs", (char *)mntdir, "devtmpfs", MS_SILENT, NULL);
372 if (err)
373 printk(KERN_INFO "devtmpfs: error mounting %i\n", err);
374 else
375 printk(KERN_INFO "devtmpfs: mounted\n");
376 return err;
377}
378
379static DECLARE_COMPLETION(setup_done);
380
381static int handle(const char *name, umode_t mode, struct device *dev)
382{
383 if (mode)
384 return handle_create(name, mode, dev);
385 else
386 return handle_remove(name, dev);
387}
388
389static int devtmpfsd(void *p)
390{
391 char options[] = "mode=0755";
392 int *err = p;
393 *err = sys_unshare(CLONE_NEWNS);
394 if (*err)
395 goto out;
396 *err = sys_mount("devtmpfs", "/", "devtmpfs", MS_SILENT, options);
397 if (*err)
398 goto out;
399 sys_chdir("/.."); /* will traverse into overmounted root */
400 sys_chroot(".");
401 complete(&setup_done);
402 while (1) {
403 spin_lock(&req_lock);
404 while (requests) {
405 struct req *req = requests;
406 requests = NULL;
407 spin_unlock(&req_lock);
408 while (req) {
409 struct req *next = req->next;
410 req->err = handle(req->name, req->mode, req->dev);
411 complete(&req->done);
412 req = next;
413 }
414 spin_lock(&req_lock);
415 }
416 __set_current_state(TASK_INTERRUPTIBLE);
417 spin_unlock(&req_lock);
418 schedule();
419 }
420 return 0;
421out:
422 complete(&setup_done);
423 return *err;
424}
425
426/*
427 * Create devtmpfs instance, driver-core devices will add their device
428 * nodes here.
429 */
430int __init devtmpfs_init(void)
431{
432 int err = register_filesystem(&dev_fs_type);
433 if (err) {
434 printk(KERN_ERR "devtmpfs: unable to register devtmpfs "
435 "type %i\n", err);
436 return err;
437 }
438
439 thread = kthread_run(devtmpfsd, &err, "kdevtmpfs");
440 if (!IS_ERR(thread)) {
441 wait_for_completion(&setup_done);
442 } else {
443 err = PTR_ERR(thread);
444 thread = NULL;
445 }
446
447 if (err) {
448 printk(KERN_ERR "devtmpfs: unable to create devtmpfs %i\n", err);
449 unregister_filesystem(&dev_fs_type);
450 return err;
451 }
452
453 printk(KERN_INFO "devtmpfs: initialized\n");
454 return 0;
455}